Fracturing involves pumping large volumes at high pressure into a formation to initiate and extend fractures and later to extract hydrocarbons. The material that is pumped is invariably water with a small percentage by weight of solids such as proppants that are used to create and hold open the produced fractures with the high pressure associated with the slurry flow.
In the past the slurry was prepared at the surface using a mix tank connected to a water line. The solids were tossed into the top of the tank and significant horsepower was needed to drive one or more agitators to keep the solids from precipitating in the tank and to maintain a slurry of uniform consistency for the fracturing process that occurred at the subterranean location. The slurry would then be delivered to an inlet of a triplex pump to deliver the requisite volume and the needed pressures. These pumps are large 3 cylinder piston pumps driven by a diesel engine although more recently natural gas driven engines have been used.
Pumps that deliver solids into fluid piping systems have been used primarily in the coal fired utility industry and are marketed by General Electric Company under the trademark Posimetric®. These pumps are described and deployed in U.S. Pat. No. 8,307,975; US Publication 20120027663 and US Publication 2012/0107058.
The use of a mix tank with agitators presents issues of space that can be in short supply at some well locations as well as maintenance and operational consistency issues. The present invention seeks improve the systems for slurry preparation for use in subterranean operations, notably fracturing by elimination of the mixing equipment described above and using a solids pump to deliver to the suction or discharge of a fracturing pump that also receives the fluid supply. These and other aspects of the present invention will become more readily apparent to those skilled in the art from a review of the detailed description and the associated FIGURE while recognizing that the full scope of the invention is to be determined from the appended claims.